Hi Jeff,
First, a caution: I'm a long way from flying, so this is untested
in flight.
But I did a similar thing to what Bobby said, and used a leaf
blower to pressurize my rad plenum. I used a thread on a stick to
check outflow from the rad core. Looking at the drawing of your
wedge plenum, I'd bet that almost all the air is coming out the
last 5 or 8 inches of the core. Before I made mine, I asked Tracy
about his RV-8 plenum. He said to pinch the back down tight; that
he had to stuff open cell foam in the back of his to even the
flow, so I did (I thought). He happened to be here as I was
getting ready to glass the mold, and commented that it was
probably too thick at the rear. (It was *much* tighter than your
drawing shows.) Sure enough, when I checked flow, all the air came
through the rear of the core. To get even flow from front to back,
I re-shaped the inside of the wedge until the last couple of
inches almost touch the core.
Also, in order to spread flow across the core (side to side,
perpendicular to the inlet flow), I had to install a turning vane
in the inlet duct. For reference, I'm building an RV-7 with a Sam
James cowl made for a Lyc; not the rotary cowl with a chin inlet
for the rad. So my ~4.5" round inlet transitions to more or less
rectangular cross section with slightly increased area where it
arrives at the front edge of the core. Then it's a concave wedge,
pinching down to almost a knife edge at the back end of the core.
No idea if it will actually cool, but I do know that the airflow
coming out of the core is pretty evenly balanced when using the
leaf blower to push air through it.
Pics below. The trailing edge is a lot thinner than it looks,
because there's 'filler' on the inside to thin the wedge.
FWIW...
Charlie
http://s1155.photobucket.com/user/rv7charlie/media/1d6b1e19.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/slobovia12a_zps3194777e.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/pdrop2012_zpscbc0ae13.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/4seatback_zps033399e2.jpg.html
http://s1155.photobucket.com/user/rv7charlie/media/Slobovia14_zps413ea84e.jpg.html
On 5/15/2015 2:17 PM, Jeff Whaley wrote:
Actually
I don’t have any really good pictures because I took it
apart … but attached is a side-view after removal of the
inlet diffuser on top and also a sketch of approximate scale
and shape of what I tried to make, (I don’t have a damper
plate or cowl flap yet). The top shape isn’t quite right;
needs to be pinched more at the rear, also am considering a
turning vane to direct more air through the front half.
Trying to make air bend 90 degrees twice isn’t easy but I
chose this orientation because of the desire to add a damper
at the output for winter operations. I could drop the rear
of radiator and bring air in through the bottom, spilling
out over the engine but would lose the ability to have a
damper – I don’t like the idea of inlet dampers. On top of
it all, my climb speed is usually only 90 mph; I don’t have
the ability to get extra pressure from increased airspeed.
P.S. the radiator is the Griffin 2-58185-X, same as
several other installs on this list.
The
top plenum was out in the SUV; hopefully more attachments in
next post …
Jeff
|
|
|
Sorry to hear that Jeff. My
apologies if you have already posted pictures of the
your installation and the diffuser, but could you post
some now?
Dave Leonard
On Fri, May 15, 2015 at 8:19 AM,
Jeff Whaley <flyrotary@lancaironline.net>
wrote:
|
From:
Jeff Whaley
Sent: Friday, May 15, 2015 11:19 AM
To: 'Bobby J. Hughes'
Subject: Return to Flight - 2
Well,
the second flight occurred last night with same results as
before; one short low-level circuit due to insufficient
cooling … looks like Al Wick made the correct prediction.
There
are 3 things I can try with the current configuration: 1)
Increase inlet area 2) Increase outlet area (adjustable cowl
flap) 3) Re-profile the pinched diffuser. I will do all 3
and see what happens.
If
all of the above show remarkable improvement then
repositioning the radiator is the only alternative.
Jeff
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